An electrical load which receives power through an AC power system is generally designed to operate reliably when the actual supply input voltage is within approximately 10% of the rated supply input voltage. A voltage sag (or dip) can refer to a temporary reduction of the rms AC voltage in which the actual supply input voltage is below approximately 90% of the rated supply input voltage. A dynamic voltage sag correction device can refer to a device which is capable of correcting temporary voltage sags in a voltage input signal that is being provided to a load. Voltage sags can be caused by startup of a large load within a facility, a circuit fault a problem at a utility company, a problem with a generator, or any of a number of other reasons. The dynamic voltage sag correction device is generally inserted between the voltage input and the load, and includes a combination of circuit elements and logic which are adapted to provide a correction signal almost instantaneously.
Traditional dynamic voltage sag correction devices are packaged according to their current and voltage ratings. For example, a first dynamic voltage sag correction device for a three-phase input voltage may be rated for 100 amps (A) at 277 volts (V), and have a corresponding kilovolt ampere (kVA) rating of ((277 V)*(100 A)*(√3))/1000=48.0 kVA. A second dynamic voltage sag correction device for a three-phase input voltage may be rated for 100 A at 120 V such that its kVA rating is 20.8 kVA. Because components in a dynamic voltage sag correction device are selected primarily according to the current rating, the first and second dynamic voltage sag correction devices are similar in physical size, components used, and cost. In other words, the second dynamic voltage sag correction device with a kVA rating of 20.8 kVA costs almost as much as the first dynamic voltage sag correction device with a kVA rating of 48.0 kVA Traditional manufacturers generally make a distinct dynamic voltage sag device for each distinct input voltage.
Manufacturing a distinct dynamic voltage sag correction device for each distinct input voltage also increases the cost of manufacturing. For example, a first dynamic voltage sag correction device with a 208 V rating may be manufactured for use only with a 208 V input, a second dynamic voltage sag correction device with a 240 V rating may be manufactured for use only with a 240 V input, and so on. Each of these differently rated dynamic voltage sag correction devices require different parts and are manufactured and packaged separately. As a result, dynamic voltage sag correction device manufacturers are required to purchase and inventory parts for a plurality of different devices. Manufacturing costs would be reduced if a single dynamic voltage sag correction device could be adapted for use with a plurality of input voltages.
In some instances, dynamic voltage sag correction devices are used at a fraction of their ratings. For example, a dynamic voltage sag correction device with a three-phase voltage rating of 480 V (in a 277 V line-to-neutral system) may be used in a system which is supplied by an input voltage of 208 V (in a 120 V line-to-neutral system). As a result, the kVA throughput of the dynamic voltage sag correction device is reduced below its rating. Traditional dynamic voltage sag correction devices are further limited in their ability to accept higher input voltages such as a 600 V line-to-line signal. To handle these high voltages, specialized heavy duty devices are manufactured. The specialized devices are manufactured and packaged separately from lower voltage dynamic voltage sag correction devices, resulting in additional costs and the need to inventory additional parts.
Thus, there is a need for a dynamic voltage sag correction device in which optimal utilization of the kVA capability of the device can be achieved regardless of the input voltage. Further, there is a need for a dynamic voltage sag correction device which can be configured for use with a plurality of distinct input voltages. Further, there is a need for a high voltage dynamic voltage sag correction device which is able to provide a correction signal in an even higher voltage system.